i) Field of the Invention
The present invention relates to a navigation system to be mounted on vehicles for giving necessary information to a driver before and during driving.
ii) Description of the Related Art
A variety of equipment has heretofore been proposed for giving necessary information to a driver and offering the promise of comfortable driving. As one example of such equipment, a navigation system is well-known and has been installed on various kinds of vehicles. Also, various kinds of navigation systems have been developed, for example, one which simply displays map information on a display, another one exhibiting a present position of a driver's own vehicle on a map, and a further one which not only searches for the shortest route from a present position to a destination and displays it on a map, but also continuously guides along driven routes, together with indicating the present position of a vehicle while driving. By using such a navigation system, the driver can readily recognize the route up to the destination and the driver's load when driving can be reduced.
Further, as disclosed in Japanese Patent Laid-Open No. Hei 2-278116, a navigation system displaying the quickest route from a starting place to a destination, the shortest route and the route having the best fuel consumption rate has been developed. That is, in this case, the necessary time, traveling distance and fuel consumption of every section between intersections are stored in a database, and by using this database, necessary time, traveling distances and fuel consumption of a plurality of routes from the present position to the destination are calculated. Then, the routes to the destination being quickest, shortest, and having the best consumption rate are displayed. Hence, the driver can select any route and decide the route depending on his situation at that time. Consequently, the driver can decide which route matches his requirements at that time.
However, when a driver actually commences driving, he has a lot of requirements such as information about how much time it takes to reach a destination, and of whether or not refueling is required on the way, and information about which places can be reached in, for example, about two hours, and further about department stores reachable within 30 minutes. In the conventional navigation system, these requirements are not considered at all and thus no routes satisfying these requirements can be given. Also, time and necessary fuel are varied depending upon the extent of traffic congestion and the like, and it is preferable to enable the driver to take such factors into consideration. Further, there may be a requirement such as wanting to obtain information concerning what methods can be considered in order to reach the destination within a predetermined time.